1. Field of the Invention
The present invention relates to a filtering apparatus for an electronic musical instrument which varies tone volume and tone color of a musical tone in a manner similar to that of an acoustic musical instrument.
2. Prior Art
Conventionally, an electronic musical instrument provides an envelope generator (hereinafter referred to as xe2x80x9cEGxe2x80x9d) which generates an envelope signal controlling the tone volume and the tone color of the musical tone signal, and memory storing data for controlling tone parameters concerning the tone volume and tone color by use of the EG. An example of such electronic musical instrument has been disclosed in U.S. Pat. No. 4,301,704, which application was filed by the same applicant of the present invention.
When the player depresses a key of a keyboard and the like, the electronic musical instrument reads out the data for controlling the tone parameter from the memory in response to a keycode corresponding to the depressed key, and then changes the tone volume and the tone color of the musical tone signal on the basis of the read-out data.
However, since the data for controlling the tone parameter is stored in the memory in advance, the variations of the tone volume and the tone color must be limited.
In addition, the parameters are respectively set by each tone color and tone pitch. Therefore, the conventional electronic musical instrument needs a large memory to store the data for controlling the parameters.
It is accordingly a primary object of the present invention to provide a filtering apparatus for an electronic musical instrument in which the tone parameter can be controlled easily by the player without enlarging the size thereof.
It is another object of the present invention to provide a filtering apparatus for an electronic musical instrument which can offer complicated variation of the tone color and generate the musical tone with a high degree of freedom.
Filtering apparatus for an electronic musical instrument, in accordance with the invention, includes cutoff frequency setting means for setting a cutoff frequency and filter parameter designating means for designating a plurality of control points for changing the cutoff frequency relatively in accordance with a lapse of time. Filter controlling means generates a filter control signal in response to the cutoff frequency and the control points. The cutoff frequency and the control points are supplied from the filter parameter designating means and change with the lapse of time. A digital filter effects a filtering operation on a musical tone signal inputted thereto. The filter has a frequency characteristic determined by the filter control signal.
Further in accordance with the invention, filtering apparatus for an electronic musical instrument comprises tone generating means for generating a tone signal having a predetermined pitch, cutoff frequency setting means for setting a cutoff frequency of filtering, and filter designating means for determining a plurality of control points changing relatively with a lapse of time, defining a segment between two adjacent control points, and generating a filter parameter by carrying out an interpolation operation between two adjacent control points. Controlling means generates a filter control signal in response to the cutoff frequency and in response to the information supplied from the filter designating means. The information changes with the lapse of time, and the controlling means changes a speed, in accordance with a tone pitch, at which the filter control signal is varied for at least one of the segments.
Still further in accordance with the invention, filtering apparatus for an electronic musical instrument comprises a digital filter having a frequency characteristic to be varied in a lapse of time and determined by a filtering parameter for effecting a filtering operation on a musical tone signal inputted thereto. Assignment means enables a player of the electronic musical instrument to assign a plurality of control points, each corresponding to the filtering parameter and to a cutoff frequency of the filter. Controlling means changes the filtering parameter and a variation manner of the frequency characteristic to be varied in a lapse of time in accordance with a limit set according to the cutoff frequency.
Still further in accordance with the invention, filtering apparatus for an electronic musical instrument for generating musical tones comprises tone designating means for designating generation of the musical tones and ending of the musical tones. Tone generating means generates a musical tone having a predetermined pitch in accordance with an output of the tone designating means. Filter parameter designating means varies a filtering parameter, wherein the filter parameter designating means enables a player to set a plurality of control points each corresponding to the filtering parameter with respect to a lapse of time. A filtering parameter corresponding to a point to be inserted between two adjacent control points is obtained by carrying out an interpolation operation with respect to the key code. Filter means filters the musical tone based on the parameters.